Move blood_splat out of Core.cpp
Remove bloodsplatter global variable

Was always the same as bloodsplat[0].
Remove EERIEAddTriangle, use batcher directly
Remove unused parameter from ARX_DrawPrimitive()
Split up ARX_DrawPrimitive()
Use drawTriangle() in ARXDRAW_DrawPolyBoom()
Reimplement PARTICLE_SUB2 as a single blend

This isn't *exactly* the same as the original, but I think it looks
better than the black blood we have now.